# 【LeetCode】 263. Ugly Number

## Description
> Write a program to check whether a given number is an ugly number.

> Ugly numbers are positive numbers whose prime factors only include `2`, `3`, `5`.

> Note:
> * `1` is typically treated as an ugly number.
> * Input is within the 32-bit signed integer range: `[−2^31, 2^31 − 1]`.

> 寫一個程式去確認給予的數字是否為醜數。

> 醜數是指一個正整數它的質因數只有包含`2`、`3`、`5`。

> 注意：
> * `1`是一個醜數。
> * 輸入數字是32位元的有號整數，其範圍為`[−2^31, 2^31 − 1]`。

## Example:

Example 1:

Input: 6
Output: true
Explanation: 6 = 2 × 3
Example 2:

Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2
Example 3:

Input: 14
Output: false 
Explanation: 14 is not ugly since it includes another prime factor 7.

## Solution

* 用`%(modulo)`去判斷是否可以整除。
* 用`while`去不停地除。
* 記得判斷是否為整數。

### Code

class Solution {
public:
    bool isUgly(int num) {
        if(num <= 0) return false;
        while(!(num % 2))
            num /= 2;
        while(!(num % 3))
            num /= 3;
        while(!(num % 5))
            num /= 5;
        return num == 1;
    }
};

###### tags: `LeetCode` `C++`